Perhaps Voldemort believes Harry is his property due to some dark magic ritual that went wrong. However, instead of being a passive victim, Harry starts to subtly influence Voldemort's decisions from within his 'ownership', changing the course of the dark wizard's plans. For example, he could make Voldemort overconfident in certain battles, leading to his downfall in a different way than in the original story.
A possible plot could be that Harry is magically bound to Voldemort as his property, but the bond gives Harry access to some of Voldemort's powers or knowledge. Harry then has to navigate this strange situation, trying to use what he gains to ultimately defeat Voldemort. He might have to pretend to be compliant while secretly plotting against him, and along the way, he could learn more about the dark side of magic and how to counter it.
One possible plot could be that Voldemort thinks he has a claim on Harry because of some ancient magic or prophecy, but Harry uses this false sense of ownership to his advantage to get closer to Voldemort and find his weaknesses.
One possible plotline could be that Voldemort captures Harry early on and instead of killing him, decides to keep him as a pet. Harry, being in this strange situation, might start to develop a warped sense of loyalty to Voldemort over time.
One possible plot could be that Harry is magically compelled to submit. Voldemort might use some dark magic or a powerful artifact to control Harry's mind. Another plot could be that Harry submits out of a false belief that it will save his friends. For example, Voldemort could deceive Harry into thinking that if he surrenders, his friends will be spared. Or perhaps Harry is so worn down by the fight that he gives in, thinking there's no other way, and then the story could explore how Voldemort uses Harry's submission to his advantage, like making Harry a tool to gain the loyalty of other wizards.
Yes, it can be considered dark. The idea of one character being another's 'property' implies a lack of freedom and a power imbalance that goes against the themes of equality and self - determination in the original 'Harry Potter' series.
Well, perhaps the plot could involve a magical force that binds Harry and Voldemort together because of their past relationship. Harry might then be torn between his loyalty to his friends and the pull he feels towards Voldemort. Voldemort, on the other hand, could be using this connection to manipulate Harry, or he could also be experiencing genuine feelings that he doesn't fully understand. This could create a complex web of relationships and power struggles within the story.
One possible plot could be Harry trying to understand Voldemort's past and motives through the letters. Maybe he writes to ask about Voldemort's childhood, what led him to become so evil. Another could be Harry attempting to persuade Voldemort to change his ways, using the letters as a form of communication to reach the dark wizard's humanity. Or perhaps Harry writes to taunt Voldemort, using the fanfiction as a way to get under his skin and make him angry in a psychological battle.
One possible plot is that Harry discovers a hidden prophecy that says only by helping Voldemort can he truly save the wizarding world in the long run. So, he reluctantly starts to assist Voldemort in his conquests, all while secretly planning to turn the tables.
Perhaps Voldemort, in his quest for ultimate power, realizes that having Harry under his control would be a great asset. He manages to enslave Harry through a combination of dark magic and psychological manipulation. Harry is then made to serve Voldemort in his lair. He could be tasked with brewing dark potions or training young Death Eaters. Meanwhile, Harry's friends suspect something is wrong and start an investigation. Harry, deep down, still has his own will and tries to leave clues for his friends to find him and break the enslavement. The story could be full of tense moments as Harry tries to resist while being under Voldemort's constant watch.
In this fanfiction, Harry as Voldemort's snake would likely have some unique powers. Snakes are known for their acute sense of smell, so Harry might be able to track things or people with great precision. He could also have the ability to hypnotize his prey or those he wants to manipulate, just like a real snake. Since he is related to Voldemort in this strange way, he might also gain some magical protection. Voldemort would probably not want his 'pet' to be easily killed, so he might place some spells on Harry that give him an added layer of defense. This could make Harry a more formidable presence, both as a snake and potentially if he were to regain his human form later.
It could be that the pet is magically attracted to the glasses. Maybe the glasses have a certain charm or power that the pet senses, and it tries to steal them to bring back to Voldemort. For example, if the glasses can see through certain dark magic disguises, Voldemort would want to get his hands on them through his pet.
The pet could try to break Harry's glasses. Since Voldemort hates Harry, his pet might be programmed or trained to destroy things that are important to Harry. The glasses are a very visible and important part of Harry.